A harvester with an Integrated Harrington Seed Destructor (iHSD) attached. Photo by McIntosh & Son.
Optimising the set up and operation of a harvester is vitally important in maximising the success of most Harvest Weed Seed Control (HWSC) systems used to collect or destroy weed seeds.
And ensuring that harvesters are not travelling too fast will help prevent grain losses worth as much as $20 per hectare.
These were messages delivered by Charles Sturt University (CSU) researcher John Broster to the recent Grains Research and Development Corporation (GRDC)-sponsored Australasian Weeds Conference in Perth.
He presented findings from a GRDC-funded study aimed at determining the proportion of annual ryegrass weed seeds collected by a harvester – that then exit in the grain, straw and chaff fractions - under commercial wheat harvesting conditions.
The research was conducted in south-eastern Australian wheat crops by the Graham Centre for Agricultural Innovation – an alliance between CSU and the NSW Department of Primary Industries.
An important factor in many HWSC systems is the proportion of weed seeds exiting the harvester in the chaff fraction, with chaff carts, chaff tramlining, chaff lining, the Harrington Seed Destructor (HSD) and the Integrated Harrington Seed Destructor (iHSD) targeting this fraction only.
“Cab settings of the harvester used in the 2015 trials were adjusted to maximise the efficiency of an attached iHSD, although no physical changes were made to concaves or grates,” Dr Broster said.
Simply adjusting the settings helped to ensure that grain and weed seeds were moved out of the concave and onto the sieves and resulted in a low percentage (3.4 per cent) of annual ryegrass being lost in the ‘straw fraction’.
“This was a much better outcome compared with results from 2014 trials, where the settings of five harvesters were not adjusted and were simply what farmers were already using,” Dr Broster said.
“In the 2014 trials, an average of 49.2 per cent of annual ryegrass was lost in the straw fraction.”
Dr Broster said the most effective harvester set-up for HWSC might vary between different weed species, as trial results were different for annual ryegrass weed seeds and wild oats.
The effect of harvest speed was also investigated, with speeds of 4, 6 and 8 kilometres per hour tested in 2015.
“When harvester settings optimised the efficiency of the attached iHSD, as was the case in 2015, harvest speed did not influence the amount of annual ryegrass seed lost in the straw fraction,” Dr Broster said.
“However, increasing the harvester speed did result in increased loss of grain (5 per cent of the total amount harvested) through the straw, especially when the harvester was operating at full capacity.
“The average yield of the crop was 2.45 tonnes per hectare and at 8kph the harvester was at full capacity.
“If wheat is worth $200 per tonne the additional wheat loss at 8kph would be valued at $20 per hectare.”
Australian Herbicide Resistance Initiative communications leader Peter Newman said improving the set up of a harvester included changing settings in the cab and ‘opening up’ hardware in the harvester to help clear grain from the rotor.
Mr Newman said a video demonstrating how to ‘open up’ a harvester, featuring WA grower and HSD inventor Ray Harrington, was available at this link.
Dr Broster’s HWSC research paper – Harvest weed seed control: the influence of harvester set up and speed on efficacy in south-eastern Australian wheat crops – is available at this link.
Information on HWSC is also available at this link.
John Broster, Charles Sturt University
02 6933 4001, 0427 296 641
Peter Newman, Planfarm/AHRI
08 9964 1170, 0427 984 010
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code